Endoscopes have an insertion portion to be inserted into, for example, the body cavity of a subject body. The insertion portion is composed of a tip hard portion, a curved portion, and a soft portion which are arranged in this order from the tip. The tip surface of the tip hard portion is provided with an observation window, illumination windows, a forceps outlet, and an air/water supply nozzle. A camera module and light guides are attached to the inner wall of the tip hard portion at such positions as to correspond to the observation window and the illumination window, respectively. The curved portion is formed by connecting plural joint ring units and can thereby direct the tip hard portion to a desired direction by a wire manipulation. The soft portion has a length of 1 to 2 m to allow the tip hard portion to reach a desired observation part of a subject body.
The camera module is composed of a shooting lens unit and an imaging unit. The shooting lens unit is configured in such a manner that plural lenses are housed in a housing. The imaging unit is equipped with an image area sensor such as a CCD (charge-coupled device) or a CMOS (complementary metal-oxide-semiconductor) sensor for photoelectrically converting an optical image formed by the shooting lens unit into an image signal. The image area sensor is connected to a transmission cable via a circuit board such as a flexible board or a sub-board. The flexible board or sub-board is mounted with electronic components for driving the image area sensor. An output signal of the imaging unit is sent, via the flexible board or sub-board and the transmission cable, to an image processing device, which performs image processing on the received signal and displays an image of, for example, a lesion on the monitor.
The transmission cable which sends a signal from the imaging unit to the image processing device is a composite multicore cable. Inserted in the insertion portion over its entire length, the transmission cable is pushed and pulled strongly every time the insertion portion is looped or bent. When the transmission cable is pulled in, a problem may occur that peeling occurs at the connection portion of the transmission cable and the circuit board or the transmission cable is disconnected.
To avoid such a disconnection or peeling, in the endoscope disclosed in JP-A-2013-75026, a cable link structure is disposed in an empty space between the inner circumferential wall of a tip hard portion and an image area sensor. The cable link structure is disposed close to the image area sensor approximately parallel with it. One end portion of the cable link structure is fastened to the outer sheath of the transmission cable and the other end portion is attached to a fixing cylinder of a prism holding structure that is part of the tip hard portion. The other end portion of the cable link structure is formed with a lock nail to lock on the attachment cylinder of the prism holding structure. Therefore, even if the insertion portion of the endoscope is bent repeatedly and the transmission cable is pulled each time, since a pull is transmitted to the prism holding structure via the cable link structure, no pull acts on the circuit board etc., thus preventing peeling at the connection portion of the transmission cable and the circuit board and a disconnection of the transmission cable.